Presently, a molded product including a sub-μm ultra-minute uneven portion on a surface thereof and having a three dimensional geometry, thin wall and large-area is required for an optical part for an electronic display such as a micro-lens array or a part for optical information communication such as a multi-mode optical waveguide passage and the like.
Hereinafter, related method for manufacturing such molded product including a minute uneven portion on a surface thereof will be described.
Patent document 1 discloses an object to provide a method for efficiently manufacturing an optical molding having high optical-transparency, low birefringence and excellent mechanical strength, including a minute uneven portion and being thin wall and large area. Patent document 1 uses a press molding machine, which is composed of an upper metal mold and a lower metal mold which are spaced apart from each other and each of which includes a cavity surface. A minute uneven portion having a height or a depth of less than 50 μm is engraved on the cavity surface of one of the upper metal mold and the lower metal mold. In this method, a melted non halogen thermoplastic is supplied to the lower metal mold, and the molten resin is pressed while the temperature of the molten resin is in the temperature range of (Tg+10° C.) or higher to less than (Tg+150° C.) with respect to the glass transition temperature (Tg) of the molten resin.
Patent document 2 discloses an object to provide a manufacturing method which forms a minute uneven pattern accurately, prevents the uneven filling of a resin, enhances mold releasing efficiency and prevents the imhomogeneous temperature of a product or a molded product when it is released from a metal mold in order to obtain a bend-free, large area and thin wall molded product. According to patent document 2, a molten alicyclic polymer resin is filled into a cavity formed by a movable side metal mold, in which an inner surface thereof is coated with diamond-like carbon, and a fixed side metal mold. The molten resin is then compressed by the movable side metal mold.
Patent document 3 discloses an object to provide an efficient and high-precision method for transcribing a minute shape. Patent document 3 prepares a metal mold including a transcribe surface, on which an uneven pattern is engraved. The transcribe surface is pressed against a polymeric substrate, which is softened by heating up to a given temperature and is thereby softened. Then, the metal mold is forcibly pulled apart from the polymeric substrate at a given temperature. Accordingly, the uneven pattern is transcribed to the surface of the polymeric substrate.
Patent document 4 discloses an object to provide a method for manufacturing an optical product including an optical element such as a minute Fresnel lens shape, a minute lenticular lens shape or a minute prism lens shape with high quality and at a low cost. Patent document 4 includes a step of coating radiation-setting resin liquid over an entire surface of the minute uneven portion of a metal mold by using a slit nozzle.
Patent document 5 discloses an object to provide a minute pattern transcribing method in which forming a minute uneven pattern, which may be equal to or less than a wavelength of the light, on a transcribed member in a mass-producible manner at a lower cost. Patent document 5 prepares a transcribe member including a minute uneven pattern and pores a material which will be formed as the transcribed member onto the minute uneven pattern of the transcribe member in a state where the material is melted by heating. The poured molten material is cooled and solidified and, at the same time, the minute uneven pattern is transcribed to the solidified material. Then, the solidified material with the transcribed minute uneven pattern transcribed thereto is released from the transcribe member and is removed as the minute uneven pattern transcribed member.    Patent Document 1: JP-A-2003-211475    Patent Document 2: JP-A-2004-98580    Patent Document 3: JP-A-2001-26052    Patent Document 4: JP-A-2002-268146    Patent Document 5: JP-A-2000-39702